This invention relates to a supercharger which compresses the air, drawn thereinto from the exterior, and feeds it to an engine.
As superchargers for an automobile engine, there are well known a turbocharger, comprising an exhaust gas turbine and a centrifugal compressor, and displacement compressors (called a supercharger) such as a Roots type, a Lysholm type (screw type) and a scroll type (spiral type).
There are also known a pressure wave-type supercharger, which compresses intake air, utilizing pressure waves of exhaust gas, and a supercharger called a complex device. These are described in detail, for example, in "In Search For Ultimate Engine, Second Series" (written by Hiroshi Kanesaka, and published Feb. 20th, 1991 by Sanei Shobo).
In a turbocharger, a turbine is rotated by the pressure of exhaust gas, so that a centrifugal impeller, mounted coaxially therewith, is rotated to compress intake air. The energy, possessed by the exhaust gas, can be recovered, but the pressure of the intake air can not be sufficiently increased in a low engine speed range in which the flow rate of the exhaust gas is low.
On the other hand, in a supercharger or a pressure wave-type supercharger using a displacement compressor, the pressure of the intake air can be sufficiently increased even in a low engine speed range, but since these superchargers are driven through a belt operatively connected to the engine, or by an electric motor, part of the engine power is consumed for driving purposes.
Usually, in a pressure wave-type supercharger as disclosed in Japanese Patent Unexamined Publication Nos. 60-150427 and 4-94419, a cylindrical rotor, having a plurality of cells therein, is rotated in synchronism with the rotation of an engine, and exhaust gas is introduced into the rotor through part of one end of the rotor while intake air is introduced into the rotor through part of the other end thereof, thereby exchanging the pressures. It is said that this supercharger is suited particularly for a diesel engine, and an effective supercharging effect can be obtained even during a low-speed operation, but since the intake air and the exhaust gas are brought into contact with each other within the rotor, the partial mixing between the intake air and the exhaust gas is inevitable.
There is known the type of pressure wave-type supercharger as disclosed in Japanese Patent Unexamined Publication No. 3-182628, in which a rotor has cells inclined radially, so that a revolving force is imparted to the rotor, or a centrifugal force is exerted on intake air and exhaust gas, thereby assisting in a scavenging operation. With this construction, the cost can be reduced, but generally, the cost of the pressure wave-type supercharger of this type is high.
Next, an impeller, used in the present invention, will be described. This impeller is basically similar in construction to impellers used in a westco pump and an eddy-flow blower, disclosed for example in Japanese Utility Model Examined Publication No. 59-36715 and "Literature of Japan Mechanical Engineering Association" (Vol.40, 336 (August, 1974), p2197-2208), and impellers used in a fluid machine (disclosed in other literature) called a regenerating fluid machine, a periphery pump and so on.
Namely, this impeller basically comprises a plurality of fluid pressure-increasing blades (or vanes) formed radially on a disk-shaped base (body) at an outer peripheral portion thereof, and in one type of such impeller, the plurality of blades are formed on one side (face) of the disk at the outer peripheral portion thereof, and in the other type, the plurality of blades are formed on the opposite sides of the disk at the outer peripheral portion thereof.
In a conventional pump or a conventional blower, such an impeller is received within a casing in such a manner that a ring-like fluid passage is formed around the blades of the impeller, and one partition wall, which separates a fluid inlet and a fluid outlet from each other, is provided in the fluid passage in such a manner that the partition wall will not hinder the rotation of the impeller.
The impeller is rotated by a motor or an engine, and a fluid is drawn through the fluid inlet provided on one side of the partition wall, and the fluid is subjected to several centrifugal compression operations by the plurality of blades to be increased in pressure, and is discharged through the fluid outlet provided on the other side of the partition wall. Since the fluid is subjected to several centrifugal compression operations, there is provided a feature that the pressure can be increased greatly even at a relatively low rotational speed.